1. Download the latest version of SparkIV or OpenIV...or whatever editing program you wish to use
2. Open it
3. Open the playerped.rpf file located in X:\YourInstallationFolder\Grand Theft Auto IV\pc\models\cdimages
4. Import the file included in this archive, for every different suits
5. Save
6. Enjoy

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Note: For the brown one you must have a trainer, because that cloth can't be find in game